Topic: Investigation
Oral Presentation Language: Portuguese
Authors: Matheus L Oliveira, Polyane M Queiroz, Francisco Haiter-Neto, Francisco C
Groppo, Deborah Q Freitas
Institution: Piracicaba Dental School, University of Campinas, Brazil
INFLUENCE OF VOXEL SIZE AND FIELD OF VIEW ON THE EFFICACY OF CBCT
METAL ARTEFACT REDUCTION TOOL
Introduction and objectives: Some cone-beam computed tomography (CBCT)
units have a metal artefact reduction (MAR) tool with the purpose of reducing CBCT
image artefact formation. Selected imaging factors, such as voxel size and field of
view (FOV), are expected to affect the overall image quality, but their relation with
MAR remains unclear. Thus, the aim of this study was to evaluate the influence of
voxel size and FOV on the efficacy of MAR tool.
Methods: Two imaging phantoms were custom-made of three cylinder-shaped
objects arranged in a triangle and surrounded by acrylic resin. Each phantom had the
three objects made of the same dental material: amalgam or aluminium-copper alloy.
The imaging phantoms were CBCT scanned separately on the Picasso-Trio CBCT
unit at 80 kVp, 3.7 mA, two voxel sizes of 0.3 mm and 0.2 mm, and four FOV sizes of
120 x 85 mm, 80 x 80 mm, 80 x 50 mm, 50 x 50 mm (diameter x height). Each scan
was performed twice with and without MAR. On the OnDemand 3D software, circular
regions of interest were selected on the axial reconstructions around the cylinder of
the dental materials and in an area under no effect of them (control area). Mean grey
values, standard deviation and contrast-to-noise ratio (CNR) were obtained and
compared by Friedman’s test (Dunn’s test as post hoc) (α=0.05).
Results and discussion: Mean grey values and standard deviation showed
significant difference (p<0.05) between FOV sizes and between voxel sizes,
respectively, in the control area. Instead, no significant difference (p>0.05) was
observed between the presence and absence of MAR within the same imaging
protocol.
Conclusions: The efficacy of MAR is not influenced by voxel size and FOV. CBCT
imaging protocols should be selected based on selection criteria, regardless of the
use of MAR tool.
Keywords: Cone-beam Computed Tomography; Artifacts; Photon Absorptiometry;
Densitometry